Rangwali Holi, the morning after the bonfire. Purnima still holds at sunrise that day, so dating it as Chaitra Krishna Pratipada puts it a day late — the relationship to Holika Dahan is the definition.
Holi is the day after Holika Dahan.
Computed from the Moon’s elongation with the Swiss Ephemeris, sidereal, Lahiri ayanamsa. A tithi begins and ends at a real minute rather than at midnight, which is why the moment above decides the day — and why the same tithi read at a different hour can name a different date.
Cast a free kundli, or ask any of 24 astrologers what this year actually holds for you. Billed by the minute, and only while somebody is answering.